Psoriasis is a chronic inflammatory skin disease of unknown cause, characterized by the development of reddish patches of skin covered with silvery-white imbricated scales. The disease generally affects the extensor surfaces of the body, along with the back and the scalp. It is believed that the disease is determined in part by a genetically dominant trait. Psoriasis is generally not seen at birth, but can begin at any age from early childhood to extreme old age, and is normally most severe between the ages of 10 and 50. The disease does not appear to be communicable, and environmental causes are not apparent. Factors often influencing psoriasis include local trauma, preceding mild inflammatory diseases, psychosomatic factors, and climate, especially low relative humidity.
While several treatments are currently available for psoriasis, no therapeutic method assures a cure. Prolonged use of any agent usually reduces its effectiveness. Agents commonly used in treating psoriasis include coal tar, ammoniated mercury, anthralin, and topical corticosteroids such as fluocinolone acetonide, fluorandrenolide, and triamcinolone acetonide. Methotrexate has been used systemically in the treatment of severe and extensive psoriasis; however, its extreme toxicity is generally a limiting factor in its use. Antimetabolite drugs such as aminopterin, thioguanine, and Azaribine have also been used.
Extensive research has been directed toward finding better methods of treatment, and even potential cures, for psoriasis. An effective topical treatment would be especially useful and desirable. Comaish and Juhlin have indicated that while methotrexate is useful in treating psoriasis systemically, it is not successful when used topically; Arch. Dermatol., 100, 99 (1969). Only one antimetabolite, fluorouracil, has been claimed to be topically effective against psoriasis; Z. Haut. Geschlechtskrankh, 44, 361 (1969).
Pyrazofurin is a C-nucleoside antimetabolite obtained initially by fermentation of a strain of Streptomyces candidus. The isolation and characterization of pyrazofurin is described in detail in U.S. Pat. No. 3,674,774. The generic name pyrazofurin replaces the generic name pyrazomycin in accordance with nomenclature adopted by the United States Adopted Names Council. This C-nucleoside has demonstrated utility as an antifungal and antibacterial agent. In accordance with this invention, pyrazofurin is useful in treating psoriasis, and is especially useful when applied topically due to its almost complete topical absorption properties.
It is an object of the present invention to provide a new and improved method for treating psoriasis, which method comprises administering pyrazofurin to a patient afflicted with the disease, the administration being either topical, oral, or parenteral, or by a combination of these routes.